Range and conservation updates for the Critically Endangered blue-eyed black lemur Eulemur flavifrons and the Vulnerable black lemur Eulemur macaco

The Critically Endangered blue-eyed black lemur Eulemur flavifrons of north-western Madagascar is one of the most threatened primates. The majority of research and conservation efforts for the species have been restricted to the Sahamalaza Peninsula but there are unstudied and unprotected populations farther inland. The dearth of information regarding the transition between E. flavifrons and its parapatric sister species, the Vulnerable black lemur Eulemur macaco, and the possibility of a hybrid population complicates conservation planning for both species. We surveyed 29 forest fragments across both species’ ranges to investigate the boundary between the taxa, whether hybrids persist, and the threats to lemurs in the region. We found E. flavifrons in six fragments and E. macaco in 17. We never observed E. flavifrons and E. macaco in the same location and we found no conclusive evidence of hybrids. Three fragments in which E. flavifrons was present were north of the Andranomalaza River, which had previously been considered the barrier between the two species. Based on these observations and a literature review, we provide updated ranges, increasing the extent of occurrence (EOO) of E. flavifrons by 28.7% and reducing the EOO of E. macaco by 44.5%. We also evaluate the capacity of protected areas to conserve these lemurs. We recommend additional surveys and the implementation of an education programme in this region to help conserve both species.

A natural point mutation in the bitter taste receptor TAS2R16 causes inverse agonism of arbutin in lemur gustation

Bitter taste enables the detection of potentially harmful substances and is mediated by bitter taste receptors, TAS2Rs, in vertebrates. Few antagonists and inverse agonists of TAS2Rs have been identified, especially natural compounds. TAS2R16s in humans, apes and Old World monkeys (Catarrhini, Anthropoidea) recognize β-glucoside analogues as specific agonists. Here, we investigated responses of TAS2R16 to β-glucosides in non-anthropoid primates, namely lemurs (Lemuriformes, Strepsirrhini). Salicin acted as an agonist on lemur TAS2R16. Arbutin acted as an agonist in the ring-tailed lemur ( Lemur catta ) but as an inverse agonist in black lemur ( Eulemur macaco ) and black-and-white ruffed lemur ( Varecia variegata ). We identified a strepsirrhine-specific amino acid substitution responsible for the inverse agonism of arbutin. In a food preference test, salicin bitterness was inhibited by arbutin in the black lemur. Structural modelling revealed this locus was important for a rearrangement of the intracellular end of transmembrane helix 7 (TM7). Accordingly, arbutin is the first known natural inverse agonist of TAS2Rs, contributing to our understanding of receptor–ligand interactions and the molecular basis of the unique feeding habit diversification in lemurs. Furthermore, the identification of a causal point mutation suggests that TAS2R can acquire functional changes according to feeding habits and environmental conditions.

Neoplasia in Prosimians: Case Series from a Captive Prosimian Population and Literature Review

Neoplastic diseases in prosimians have been sporadically reported in the literature. To provide a comprehensive review of prosimian neoplasia, a retrospective evaluation of neoplasia in a large captive prosimian colony and an extensive literature review were performed. Primates that belong to the Order Primata, Suborder Prosimii with histologic evidence of neoplasia were included. One hundred twenty-three cases of spontaneous neoplasia were identified in 101 prosimians from the Duke Lemur Center, and 124 cases were reported in 116 prosimians in the literature. Overall, this review compiled a total of 247 neoplasms in 217 prosimians. Of the 217 affected animals, 88 of 217 were males (41%), 100 of 217 were females (46%), and sex was not reported in 29 of 217 (13%). Ages ranged from 2 days to 36 years. Prosimian families represented were Lemuridae (80/217 [37%]), Cheirogaleidae (61/217 [28%]), Galagidae (44/217 [20%]), Lorisidae (28/217 [13%]), and Indriidae (4/217 [2%]). The most commonly affected species were the gray mouse lemur (Microcebus murinus) (28/217 [13%]), thick-tailed greater bush baby (Otolemur crassicaudatus) (23/217 [11%]), and black lemur (Eulemur macaco) (19/217 [9%]). Organ systems affected, in order of descending occurrence, were digestive (75/247 [30%]), reproductive (40/247 [16%]), hematopoietic (34/247 [14%]), integumentary (28/247 [11%]), endocrine (26/247 [11%]), and urinary (17/247 [7%]). The respiratory, nervous, musculoskeletal, and cardiovascular systems were infrequently affected. The most common neoplasms were hepatocellular (32/247 [13%]), lymphoma and/or leukemia (29/247 [12%]), biliary (15/247 [6%]), and mammary neoplasms (12/247 [5%]). This article should serve as a valuable reference for the types and relative frequencies of neoplasms that occur in prosimian species.